Method of call trace on media gateway of next generation network

ABSTRACT

The present invention discloses a method of call trace on an NGN MG. According to the present invention, the softswitch device adds an extended trace indication to an H.248 message related to the call to be traced; the MG determines whether the received H.248 message needs to be traced according to the extended trace indication; and if the H.248 message needs to be traced, trace the call to which the transaction in the H.248 message belongs. By the method, the MG can trace the entire calling process of a call.

This application is a continuation of International Patent ApplicationNo. PCT/CN2005/001224, filed Aug. 10, 2005, which claims priority toChinese Patent Application No. 200410059166.7, filed Aug. 11, 2004, allof which are hereby incorporated by reference.

FIELD OF THE TECHNOLOGY

The present invention relates to next generation network (NGN)technology, and more particularly, to the technique for tracing a callprocess on a media gateway (MG) in NGN.

BACKGROUND OF THE INVENTION

Conventional communication networks for transmitting voice signals areusually based on Public Switched Telephone Network (PSTN) using a TimeDivision Multiplexing (TDM) technique. This kind of communicationnetwork gives priority to circuit switching, and voice services aretransmitted and controlled by switches. The structure of a switch in aconventional TDM-based circuit switching network is shown in FIG. 1,wherein Signaling System 7 (SS7) is widely used in call controlling.

Along with a fast development of data services, conventional circuitswitching networks bring much inconvenience to data service users, suchas a high communication cost, a low net surfing speed, a long waitingtime, a poor transmitting quality, and difficulties of implementing newservices. On the other hand, along with the development of communicationtechniques, it becomes more and more possible that one data network isthe bearer of all services. It is in such a situation that the NGN isput forward and has seen fast development in recent years. The NGN hasgradually changed the conventional PSTN circuit switching based networkto a packet switching based network. This kind of packet switching basednetwork can carry all kinds of services of the previous PSTN network,and at the same time, offload a great deal of data transmission to anAsynchronous Transfer Mode (ATM)/Internet Protocol (IP) network torelease the burden of the PSTN. Moreover, based on new properties ofATM/IP, many new services are provided and functions of many oldservices are enhanced. In this sense, the NGN is an outcome of combiningthe TDM based PSTN voice network and the ATM/IP based packet network,which makes it possible to transmit voice, video, data and otherintegrated services in one new network. Moreover, the NGN adopts asoftswitch technique in which service control is separated from mediaservice bearers, which greatly enhances the processing capability ofnetwork equipments so that more voice services can be processed and thenetwork can be the bearer of more kinds of services.

International Telecommunication Union-Telecommunication StandardizationSector (ITU-T) gave the following definitions of the NGN in February,2004: the NGN is a packet network, which provides various servicesincluding telecommunication services, and can implement a separation ofservice functions from bottom-layer transmitting techniques by means ofvarious bandwidths and transmitting techniques with the capability ofQuality of Service (QoS); the NGN allows users to freely access networksof different service providers, and supports a universal mobility, whichbrings consistency and unity in use of the services by users.

A physical model of the NGN which adopts softswitch technique is shownin FIG. 2. The softswitch in FIG. 2 controls MGs through a controlprotocol such as H.248/Media Gateway Control Protocol (MGCP). The SS7only runs on the softswitch, and the H.323/Bearer Independent CallControl (BICC)/Session Initiation Protocol (SIP) and other protocolsalso run on the softswitch while each MG only performs resourceoperations.

According to the H.248 protocol, the media resource operations on the MGare performed by taking a termination as an operating unit, andtermination operations are mainly performed in a context.

The message transmission mechanism of the H.248 protocol is shown inFIG. 3. Those skilled in the art would know that the basic operationunit of an H.248 protocol message is a transaction, which includesseveral operations to the context and the terminations. A transaction isuniquely identified by a transaction ID (a long word of 32 bits). Acombination of several transactions of the softswitch will comprise allthe H.248 commands of an entire calling process.

In the MG operations based on H.248 messages, a process of addingterminations T1 and T2 and deleting T2 in a context C1 is shown in FIG.4. In the figure, the words shown above each arrow illustrates the H.248message used in each step while the words shown below each arrow givesan explanation of the corresponding H.248 message used in this step.

Detailed description of the H.248 protocol can be found in “MegacoProtocol Version 1.0□RFC3015□” or ITU-T H.248 Specification.

In the above process, once a fault, such as a call setup failure,occurs, the MG must trace the entire process of the call, and output theinteracted H.248 messages and the internal resource operations so as tolocate and solve the fault. However, since the number of calls andresource operations implemented in an MG is huge, and the timing ofthese calls and resource operations is interleaved, if information ofall the interacted H.248 messages and internal resource operations areoutputted, the signaling interaction of the entire process of each callcan not be distinguished. Therefore, filters have to be set so that onlythe signaling interaction of H.248 messages and internal resourceoperations associated with the call being traced are output.

In the prior art, in order to trace a call on an NGN MG, two technicalschemes are often used, wherein both the schemes involve creating atrace task and setting tracing conditions in the MG manually. Theimplementation of the two technical schemes is as follows:

Technical scheme 1: manually set up a trace task in the MG to trace adesignated context. After the reception of an H.248 message by the MG,analyze the context, and judge whether the call that the message belongsto needs to be traced, if the call needs to be traced, output the H.248messages received and sent and output the internal operation process ofthe MG associated to the context for use in analyzing the internalprocessing of the MG.

Technical scheme 2: manually set up a trace task in the MG to trace adesignated termination. After the reception of an H.248 message by theMG, analyze the termination in the message, and judge whether theassociated call needs to be traced, if the call needs to be traced,output the H.248 messages received and sent and output the internaloperation process of the MG associated to the termination for use inanalyzing the internal processing of the MG.

In actual applications, both of the two technical schemes have suchproblems as that the processes of some calls are difficult to trace, thedefined tracing conditions are hard to detect and a trace is difficultto implement when there are too many associated contexts or terminationsin one call and all the information of which should be outputted.

SUMMARY OF THE INVENTION

In view of the above, the present invention provides a method fortracing a call by a next generation network (NGN) MG, by which the MG iscapable of tracing the entire process of any call completely.

The method of tracing a call by an NGN MG in accordance with thisinvention includes the following steps:

a softswitch device adds an extended trace indication in the H.248message relating to the call that needs to be traced; and

the MG determines, according to the extended trace indication, whetherthe call to which the transaction in the received H.248 message belongsneeds to be traced, if yes, trace the call to which the transaction inthe H.248 message belongs.

It can be seen by comparison that the differences between the presentinvention and the prior art are that, according to the presentinvention, a trace ID is set in the H.248 message by the softswitch andcontents needing to be traced and outputted are designated, and themessage with a trace ID will be traced by the MG.

The above differences bring a few advantages, that is, since a trace IDis set by the softswitch, via which the tracing by the MG is controlled,the shortcomings brought by tracing via a designated context ortermination by the MG is overcome, and as a result, a plurality of callscan be traced at the same time, and the tracing information can beoutputted respectively and distinctively. The technical scheme of thepresent invention is simple to implement, and the H.248 messages andinternal processing traced are complete and clear. Moreover, accordingto the present invention, it is possible to output all the signalinginteraction of H.248 and the steps of internal resource operations ofthe call being traced, which makes fault analyzing and fault locatingconvenient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the structure of a switch in aconventional TDM based circuit switching network;

FIG. 2 is a schematic diagram of a physical model of the NGN adoptingthe softswitch technique;

FIG. 3 is a schematic diagram of the message mechanism in the H.248protocol;

FIG. 4 is a schematic diagram illustrating the process of addingterminations T1 and T2 and the process of deleting termination T2 in thecontext C1 through the H.248 messages and operations in the MG;

FIG. 5 is a flowchart of tracing a call by an NGN MG according to apreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, both of the two technical schemes in the prior arthave problems such as that the processes of some calls are difficult totrace, the defined tracing conditions are hard to detect and a trace isdifficult to implement when there are too many associated contexts orterminations in one call and all the information of which should beoutputted.

The reasons for the above problems are as follows: in terms of technicalscheme 1, first, for those call messages without an express designationof context, e.g. the Add.Req ($, T1) message used when the softswitchinstructs the MG to select a context by itself, if tracing of thecontext is needed in this case, the message must be buffered by the MG,until a context is allocated, and then the tracing output can beobtained after a context matching, which is very difficult to implement.

Second, it is very difficult for users to confirm the allocation ofcontexts in the MG, if an context designated by the user has beenalready allocated, the previous messages and operations are unable to betraced (except that all the history messages and operations arebuffered, which is unfeasible in practice), and if the contextdesignated by the user can not be allocated until after a long time,there will be a waste of waiting time, which makes it difficult todesignate a context.

Third, in practical applications, the processes of some calls are verycomplicated with many contexts associated, and tracing only one contextcan not give a complete reflection of the processing in the MG. Sincethe context associations are determined by the softswitch, the MG isunable to forecast the tracing relationship and unable to pre-designateeach of the contexts manually. If the context associations areimplemented by software in the MG, the processing will be made verycomplicated and the call tracing will be made difficult to implement.

Due to the same reason, technical scheme 2 has the same problems asmessages without the express information about a designated terminationare difficult to trace, designated terminations are difficult to choose,and termination associations are difficult to trace.

In order to solve the above problem, the present invention provides amethod for tracing a call by an NGN MG. And detailed descriptions of thepresent invention will be given hereinafter with reference toaccompanying drawings and preferred embodiments.

First, the basic principle of the invention will be described.

Since it is the softswitch that handles specific signaling, it is easyfor the softswitch to determine the transactions that are associatedwith a certain call. If the tracing of the entire process of the callneeds to be set up, the call can be traced just by indicating theassociated transactions to be traced in the H.248 message sent from thesoftswitch to the MG, and at the same time, the MG can output thecalling process being traced and the internal operating processes of theMG in the H.248 messages received and sent. The outputted informationwill show the entire handling process of a call in the MG.

Based on the above, the softswitch can instruct the MG to trace a callthrough an extended H.248 message communicated between the softswitchand the MG, and the MG outputs the communicated H.248 message and theinternal resource operations of the entire handling process of the callbeing traced so that the complete call tracing by an MG of the NGN canbe realized.

In order to realize the above idea, the transaction head of the H.248message is extended according to the present invention to indicate tothe MG by an on-off indicator that the call to which the transactionbelongs needs to be traced. In this way, the MG can determine whether totrace the related call at the initial stage of analyzing the H.248message, which greatly improves the efficiency. If no such an on-offtracing indicator is set, the MG needs to analyze to a deeper layer ofthe H.248 message to determine whether to trace the call, which wouldreduce the efficiency of tracing. At the same time, an H.248 calltracing extended package is defined to support the tracing of aplurality of calls simultaneously, and the package carries some contextand control information which is necessary for displaying the tracedinformation. The package can be defined in a termination statedescriptor. According to the present invention, the MG can clearlyoutput all of the calling information associating with the call beingtraced from the H.248 messages received and sent and output the relatedinternal operations of the MG. Refer to FIG. 3 for a betterunderstanding of the basic principle of the present invention as well assuch concepts as message, transaction, context, command and descriptorof the H.248 protocol and the relations there between. It should benoted that, although an H.248 message can carry a plurality oftransactions according to the H.248 protocol, most service providers,for convenience and high efficiency in implementation, carry only onetransaction in one massage and one transaction conducts operations onthe related contexts of only one call. In this case, the traced callinformation is the H.248 message itself.

If the above situation does not come into existence, e.g. there is aplurality of transactions carried in one H.248 message, the on-offtracing indicator set on the transaction head is needed in order totrace the transactions that needs to be traced. If there is a pluralityof contexts of different calls carried in one transaction, suchdifferent calls should have a logical or restricting relation betweenthemselves according to the definition of transaction in the H.248protocol. Therefore, it will be meaningful to output the information ofthe whole transaction to analyze the processing of a call concerned byusers.

A detailed description of a preferred embodiment of the presentinvention will be given hereinafter for a better understanding of thescheme of the invention.

According to the invention, the softswitch needs to extend the H.248message to be sent to the MG in order to realize call tracing by the NGNMG.

First, in the H.248 message, an on-off tracing indicator is carried viathe extended transaction head to indicate which transaction needs to betraced. According to a preferred embodiment of the present invention,the on-off tracing indicator is defined in the transaction ID. If thehighest bit of transaction ID of the message sent to the MG by thesoftswitch is set to be 1, it is indicated that the transaction needs tobe traced while the transaction need not be traced if the bit mentionedabove is set to 0, wherein 0 is the default value of the on-off tracingindicator.

Secondly, a call tracing extended package is defined in the H.248message, and the package carries identities for use in tracing multiplecalls simultaneously, and the package also carries the contentinformation and other control information that is necessary fordisplaying the output of traced information. Each termination relatingto the call that needs to be traced carries the associated contents ofthis call tracing extended package in the appropriate commands of theH.248 message when it is allowed by the protocol to carry the package.The case that no extended package is allowed to be carried will beexplained after description of the embodiment. In a preferred embodimentof this invention, the call tracing extended package is defined in thetermination state descriptor, and the main properties of this calltracing extended package can be defined as follows:

Call Trace Package

1 Overall Description

Package Name: Call trace

Package ID: trace (temporarily defined to be 0x00A0) [Editor's note:this needs to be registered with IANA]

Description: this package allows call trace function in MG to berealized useful and convenient.

Version: 1

Extends: none

2 Properties

Property Name: Trace ID

Property ID: trid (0x0001)

Description: this value is a trace ID, which is used on the gateway tostart simultaneously traces by multiple users. The call information ofthe same trace ID will be outputted to one trace window to observe thecall processing simultaneously conducted by multiple users.

Type: Integer

Possible values: 0 to 0xFFFFFFFE

Defined in: Termination State

Characteristics: Read/Write

Property Name: User information

Property ID: usrinfo (0x0002)

Description: this value is the related user information, which is theadditional information that is needed for displaying the tracedinformation in the trace window, e.g. the telephone number. At thetermination of the calling side, the calling telephone information iscarried, and at the termination of the called side, the called telephoneinformation is carried. According this information, the user informationrelating to the call information can be easily understood.

Type: List of String

Defined in: Termination State

Characteristics: Read/Write

Property Name: Trace depth

Property ID: trd (0x0003)

Description: this value is an indication of the trace depth, and thelarger the value is, the stronger the trace function is. For example, 1indicates a common grade of trace, wherein the output information onlyincludes the call information in the H.248 message needed to be tracedand the MG internal operations; 2 indicates that a tracing item is addedon the basis of 1, for example, tracing the in-band negotiationsignaling associated with the call (e.g. if fax or Modem negotiation hasbeen performed, in-band negotiation signaling on the voice path of theuser could be traced).

Type: Integer

Possible values: 1 to 10

Defined in: Termination State

Characteristics: Read/Write

Those skilled in the art could understand that, after the H.248 messageis extended according to the method mentioned above, the MG candetermine whether to trace the call information of the transactionaccording to the on-off tracing indication in the transaction head, andoutput the tracing results of different calls, respectively, accordingto the call tracing extended package carried by the H.248 message sothat all the call information and internal operations of the gatewayduring the designated call process can be traced.

The flowchart of a call trace performed by the NGN MG in a preferredembodiment of the present invention is shown in FIG. 5.

Step 110: the MG receives an H.248 message sent by the softswitch.

It should be noted that the H.248 message received in this step hasextended the current H.248 protocol, and the method of extending thecurrent H.248 protocol is the same as described above.

Step 120: the MG analyzes the message, and determines whether the callthat the transaction in the message belongs to needs to be traced, ifthe call needs to be traced, proceed to step 130, otherwise, proceed tostep 160.

In this step, whether the call needs to be traced is determinedaccording to the on-off tracing indicator carried in the transactionhead.

Step 130: the MG analyzes the H.248 call tracing extended package, andoutputs the information in the received message about the call beingtraced to a corresponding trace window according to the trace ID.

It should be noted that the call tracing extended package is inserted toa corresponding position in the H.248 message by the softswitchaccording to the need of the call that needs to be traced.

Step 140: the MG processes the commands in the message, performscorresponding resource operations, and then outputs the operationresults to the corresponding trace window according to the trace ID,wherein the information contents that need to be outputted are definedby the call tracing extended package.

Step 150: the MG sends an H.248 response message to the softswitch andoutputs the information of the call being traced to the correspondingtrace window according to the trace ID. It should be noted that theH.248 response message used in this step is completely the same as theH.248 response message in the current protocol. By now, the processingof the message that needs to be traced has been completed and theprocedure of message processing ends.

Step 160: the MG processes the commands in the message and performscorresponding resource operations.

Step 170: the MG sends an H.248 response message to the softswitch.

It should be noted that processing operations in step 160 and step 170are the processing of the messages that need not be traced, which arecompletely the same as those in the prior art. After step 170,processing of the messages that need not be traced is completed and theprocedure of message processing ends.

Those skilled in the art could understand that the Properties, Events,Signals, Statistics and other information of the call tracing extendedpackage can be further enriched, so that the tracing method could beenhanced and enriched. If no such a call tracing extended package isdefined, the call trace function can not be properly realized. It shouldbe noted in particular that the start and end of a call trace can becontrolled via signals instead of setting the on-off tracing indicatorin the transaction head of the H.248 message as mentioned in claim 2 ofthis invention while a similar effect of call trace can be obtained.However, according to this method of control a call trace via signals,the MG has to analyze to a deeper layer of the H.248 message, thus theefficiency of the call trace is relatively low.

It should be noted in addition, because of the limitations of the H.248protocol, not all the commands can carry an extended package (herein,the extended package refers to a common extended package, not thespecific call tracing extended package defined in the presentinvention). In the process of tracing the H.248 message without a calltracing extended package, the following mechanisms can be adoptedwithout affecting the call trace function.

1) As the initial commands of a call (including such commands as Add andModify) can carry the call tracing extended package, the MG canassociate such contents as the Trace ID, the User Info, and the TraceDepth in the received call tracing extended package with the TerminationID and Context ID related to the call, and make a record of theassociation.

2) In case that no extended package can be carried, the MG can look upall the related information of the call tracing extended packagecorresponding to the call being traced according to the termination IDand context ID related to the call information, so that the functions ofthe call trace will not be affected.

Although the present invention has been illustrated and described withreference to preferred embodiments, those skilled in the art understandthat modifications in form and detail could be made to such embodimentswithout departure from the spirit and scope of the present invention asdefined by the appended Claims.

1. A method of call trace on a Next Generation Network (NGN) MediaGateway (MG), comprising: receiving, by the MG, an H.248 message from asoft-switch, wherein the H.248 message is added with a trace indicatorand an Trace ID of a call that needs to be traced, wherein the traceindicator is used for indicating the MG whether the H.248 messagerelates to the call that needs to be traced, and the Trace ID is carriedin a call tracing package set for supporting simultaneous multi-calltracing; determining, by the MG, whether the call to which a transactionin the received H.248 message belongs needs to be traced according tothe trace indicator; tracing the call to which the transaction in theH.248 message belongs; and outputting different calls according to theTrace ID carried in the call tracing package respectively.
 2. The methodaccording to claim 1, wherein the trace indicator is an on-off traceindicator set in the transaction head of the H.248 message that needs tobe traced; the MG determines whether there is the on-off trace indicatorin the transaction head of the H.248 message, and determines whether totrace the information of the call to which the appropriate transactionbelongs.
 3. The method according to claim 1, wherein the call tracingpackage is carried in the H.248 message that needs to be traced; andcalling information, additional contents and destination to be tracedand to be outputted by the MG are determined by the contents of the calltracing package.
 4. The method according to claim 2, wherein the on-offtracing indicator is set in the transaction identity (ID) of the H.248message, and a default setting of the on-off tracing indicator is off.5. The method according to claim 3, wherein the call tracing packagefurther carries additional contents needed for displaying the tracingoutput.
 6. The method according to claim 4, wherein the call needs to betraced when the highest bit of the transaction ID is set to 1, while thecall need not be traced when the bit thereof is set to 0, and thedefault setting of the bit is
 0. 7. The method according to claim 3,wherein the softswitch device sets the on-off trace indicator accordingto the call that needs to be traced, and inserts the call tracingpackage to a corresponding position in the H.248 message.
 8. The methodaccording to claim 3, wherein the step of tracing the call to which thetransaction in the H.248 message belongs comprises: the MG analyzing thecall tracing extended package of the received H.248 message, andoutputting the call information to be traced in the H.248 message to thecorresponding trace window according to the Trace ID in the call tracingpackage; and the MG processing the H.248 message and implementingcorresponding resource operations, and then outputting the operationresults to the corresponding trace window according to the Trace ID inthe call tracing package.
 9. The method according to claim 8, furthercomprising: the MG sending a response message to the softswitch deviceand outputting the call information to be traced in the response messageto the corresponding trace window.
 10. The method according to claim 1,comprising outputting to one trace window different calls according tothe Trace ID carried in the call tracing package.
 11. A communicationsystem, comprising a softswitch and a media gateway which communicateswith the softswitch, wherein, the softswitch device is configured to adda trace indicator and an Trace ID of a call that needs to be traced toan H.248 message, and send the H.248 message to the media gateway,wherein the trace indicator is used for indicating the media gatewaywhether the H.248 message relates to the call that needs to be traced,and the Trace ID is carried in a call tracing packet set for supportingsimultaneous multi-call tracing; the media gateway is configured to:receive the H.248 message, determine whether the call to which atransaction in the received H.248 belongs needs to be traced accordingto the trace indicator; trace the call to which the transaction in theH.248 message belongs; and output different calls according to the TraceID carried in the call tracing package respectively.
 12. Thecommunication system according to claim 11, wherein the trace indicatoris an on-off trace indicator set in the transaction head of the H.248message that needs to be traced; the media gateway determines whetherthere is the on-off trace indicator in the transaction head of the H.248message, and determines whether to trace the information of the call towhich the appropriate transaction belongs.
 13. The communication systemaccording to claim 11, wherein the call tracing package is carried inthe H.248 message that needs to be traced; and calling information,additional contents and destination to be traced and to be outputted bythe media gateway are determined by the contents of the call tracingpackage.
 14. The communication system according to claim 12, wherein theon-off tracing indicator is set in the transaction identity (ID) of theH.248 message, and a default setting of the on-off tracing indicator isoff.
 15. The communication system according to claim 13, wherein thecall tracing package further carries additional contents needed fordisplaying the tracing output.
 16. The communication system according toclaim 14, wherein the call needs to be traced when the highest bit ofthe transaction ID is set to 1, while the call need not be traced whenthe bit thereof is set to 0, and the default setting of the bit is 0.17. The communication system according to claim 13, wherein thesoftswitch device sets the on-off trace indicator according to the callthat needs to be traced, and inserts the call tracing package to acorresponding position in the H.248 message.
 18. The communicationsystem according to claim 13, wherein the media gateway analyzes thecall tracing extended package of the received H.248 message, and outputsthe call information to be traced in the H.248 message to thecorresponding trace window according to the Trace ID in the call tracingpackage; and the media gateway processes the H.248 message andimplements corresponding resource operations, and then outputs theoperation results to the corresponding trace window according to theTrace ID in the call tracing package.
 19. The communication systemaccording to claim 18, wherein the media gateway sends a responsemessage to the softswitch device and outputs the call information to betraced in the response message to the corresponding trace window. 20.The communication system according to claim 11, wherein the mediagateway outputs to one trace window different calls according to theTrace ID carried in the call tracing package.